The present invention relates to polynucleotides isolated from a specific strain of lactic acid bacteria, namely Lactobacillus rhamnosus HN001 (L. rhamnosus HN001). Lactic acid bacteria, and their enzymes, are the major determinants of flavor and fermentation characteristics in fermented dairy products, such as cheese and yogurt. Flavors are produced through the action of bacteria and their enzymes on proteins, carbohydrates and lipids.
Lactobacillus rhamnosus strain HN001 are heterofermentative bacteria that are Gram positive, non-motile, non-spore forming, catalase negative, facultative anaerobic rods exhibiting an optimal growth temperature of 37±1° C. and an optimum pH of 6.0-6.5. Experimental studies demonstrated that dietary supplementation with Lactobacillus rhamnosus strain HN001 induced a sustained enhancement in several aspects of both natural and acquired immunity (See PCT International Publication No. WO 99/10476). In addition, L. rhamnosus HN001, and certain other Gram-positive bacteria can specifically and directly modulate human and animal health (See, for example, Tannock et al., Applied Environ. Microbiol. 66:2578-2588, 2000; Gill et al., Brit. J. Nutrition 83:167-176; Quan Shu et al., Food and Chem. Toxicol. 38:153-161, 2000; Quan Shu et al., Intl. J. Food Microbiol. 56:87-96, 2000; Quan Shu et al., Intl. Dairy J. 9:831-836, 1999; Prasad et al., Intl. Dairy J. 8:993-1002, 1998; Sanders and Huis in't Veld, Antonie van Leeuwenhoek 76:293-315, 1999; Salminen et al., 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 211-253; Delcour et al., Antonie van Leeuwenhoek 76:159-184, 1999; Blum et al., Antonie van Leeuwenhoek 76:199-205, 1999; Yasui et al., Antonie van Leeuwenhoek 76:383-389, 1999; Hirayama and Rafter, Antonie van Leeuwenhoek 76:391-394, 1999; Ouwehand, 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 139-159; Isolauri et al., S 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 255-268; Lichtenstein and Goldin, 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 269-277; El-Nezami and Ahokas, 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 629-367; Nousianen et al., 1998. In: Lactic Acid Bacteria, Salminen S and von Wright A (eds)., Marcel Dekker Inc, New York, Basel, Hong Kong, pp. 437-473; Meisel and Bockelmann, Antonie van Leeuwenhoek 76:207-215, 1999; Christensen et al., Antonie van Leeuwenhoek 76:217-246, 1999; Dunne et al., Antonie van Leeuwenhoek 76:279-292, 1999). Beneficial health effects attributed to these bacteria include the following:    Increased resistance to enteric pathogens and anti-infection activity, including treatment of rotavirus infection and infantile diarrhea—due to increases in antibody production caused by an adjuvant effect, increased resistance to pathogen colonization, alteration of intestinal conditions, such as pH; and the presence of specific antibacterial substances, such as bacteriocins and organic acids.    Aid in lactose digestion—due to lactose degradation by bacterial lactase enzymes (such as beta-galactosidase) that act in the small intestine.    Anti-cancer (in particular anti-colon cancer) and anti-mutagenesis activities—due to anti-mutagenic activity; alteration of procancerous enzymatic activity of colonic microbes; reduction of the carcinogenic enzymes azoreductase, beta-glucuronidase and nitroreductase in the gut and/or faeces; stimulation of immune function; positive influence on bile salt concentration; and antioxidant effects.    Liver cancer reduction—due to aflatoxin detoxification and inhibition of mould growth.    Reduction of small bowel bacterial overgrowth—due to antibacterial activity; and decrease in toxic metabolite production from overgrowth flora.    Immune system modulation and treatment of autoimmune disorders and allergies—due to enhancement of non-specific and antigen-specific defence against infection and tumors; enhanced mucosal immunity; adjuvant effect in antigen-specific immune responses; and regulation of Th1/Th2 cells and production of cytokines.    Treatment of allergic responses to foods—due to prevention of antigen translocation into blood stream and modulation of allergenic factors in food.    Reduction of blood lipids and prevention of heart disease—due to assimilation of cholesterol by bacteria; hydrolysis of bile salts; and antioxidative effects.    Antihypertensive effect—bacterial protease or peptidase action on milk peptides produces antihypertensive peptides. Cell wall components act as ACE inhibitors    Prevention and treatment of urogenital infections—due to adhesion to urinary and vaginal tract cells resulting in competitive exclusion; and production of antibacterial substances (acids, hydrogen peroxide and biosurfactants).    Treatment of inflammatory bowel disorder and irritable bowel syndrome—due to immuno-modulation; increased resistance to pathogen colonization; alteration of intestinal conditions such as pH; production of specific antibacterial substances such as bacteriocins, organic acids and hydrogen peroxide and biosurfactants; and competitive exclusion.    Modulation of infective endocarditis—due to fibronectin receptor-mediated platelet aggregation associated with Lactobacillus sepsis.    Prevention and treatment of Helicobacter pylori infection—due to competitive colonization and antibacterial effect.    Prevention and treatment of hepatic encephalopathy—due to inhibition and/or exclusion of urease-producing gut flora.    Improved protein and carbohydrate utilization and conversion—due to production of beneficial products by bacterial action on proteins and carbohydrates.
Other beneficial health effects associated with L. rhamnosus include: improved nutrition; regulation of colonocyte proliferation and differentiation; improved lignan and isoflavone metabolism; reduced mucosal permeability; detoxification of carcinogens and other harmful compounds; relief of constipation and diarrhea; and vitamin synthesis, in particular folate.
Peptidases are enzymes that break the peptide bonds linking the amino group of one amino acid with the carboxy group (acid group) of an adjacent amino acid in a peptide chain. The bonds are broken in a hydrolytic reaction. There is a large family of peptidase enzymes that are defined by their specificity for the particular peptides bonds that they cleave (Barrett A J, Rawlings N D and Woessner J F (Eds.) 1998. Handbook of proteolytic enzymes. Academic Press, London, UK). The two main families are exopeptidases and endopeptidases.
Exopeptidases cleave amino acids from the N- or C- terminus of a peptide chain, releasing free amino acids or short (di- and tripeptides). Different types of exopeptidases include:                Aminopeptidases—release a free amino acid from the N-terminus of a peptide chain;        dipeptidyl-peptidase (also known as dipeptidyl-aminopeptidases)—release a dipeptide from the N-terminus of a peptide chain;        tripeptidyl-peptidases (also known as tripeptidyl-aminopeptidases)—release a tripeptide from the N-terminus of a peptide chain);        carboxypeptidases—release a free amino acid from the C-terminus of a peptide chain;        peptidyl-dipeptidase—release a dipeptide from the C-terminus of a peptide chain;        dipeptidases—release two free amino acids from a dipeptide; and        tripeptidases—release a free amino acid and a dipeptide from a tripeptide.        
Endopeptidases hydrolyze peptide bonds internally within a peptide and are classified on the basis of their mode of catalysis:                serine-endopeptidases—depend on serine (or threonine) as the nucleophile in the catalytic reaction;        cysteine-endopeptidases—depend on the sulphydryl group of cysteine as the nucleophile in the catalytic reaction;        aspartic-endopeptidases—contain aspartate residues that act as ligands for an activated water molecule which acts as the nucleophile in the catalytic reaction; and        metallo-endopeptidases—contain one or more divalent metal ions that activate the water molecule that acts as the nucleophile in the catalytic reaction.Peptidases are important enzymes in the process of cheese ripening and the development of cheese flavor. The hydrolysis of milk caseins in cheese results in textural changes and the development of cheese flavors. The raft of proteolytic enzymes that cause this hydrolysis come from the lactic acid bacteria that are bound up in the cheese—either starter cultures that grow up during the manufacture of the cheese, or adventitious and adjunct non-starter lactic acid bacteria that grow in the cheese as it ripens (Law Haandrikman, Int. Dairy J. 7:1-11, 1997).        
Many other enzymes can also influence dairy product flavor, and functional and textural characteristics, as well as influencing the fermentation characteristics of the bacteria, such as speed of growth, acid production and survival (Urbach, Int. Dairy J. 5:877-890, 1995; Johnson and Somkuti, Biotech. Appl. Biochem. 13:196-204, 1991; El Soda and Pandian, J. Dairy Sci. 74:2317-2362, 1991; Fox et al,. In Cheese: chemistry, physics and microbiology. Volume 1, General aspects, 2nd edition, P Fox (ed) Chapman and Hall, London; Christensen et al., Antonie van Leeuwenhoek 76:217-246, 1999; Stingle et al., J. Bacteriol. 20:6624-6360, 1999; Stingle et al., Mol. Microbiol. 32:1287-1295, 1999; Lemoine et al., Appl. Environ. Microbiol. 63:1512-6218, 1997). Enzymes influencing specific characteristics and/or functions include the following:                Lysis of cells. These enzymes are mostly cell wall hydrolases, including amidases; muramidases; lysozymes, including N-acetyl muramidase; muramidase; N-acetylglucosaminidase; and N-acetylmuramoyl-L-alanine amidase. DEAD-box helicase proteins also influence autolysis.        Carbohydrate utilization. Lactose, citrate and diacetyl metabolism, and alcohol metabolism are particularly important. The enzymes involved include beta-galactosidase, lactate dehydrogenase, citrate lyase, citrate permease, 2,3 butanediol dehydrogenase (acetoin reductase), acetolactate decaboxylase, acetolactate synthase, pyruvate decarboxylase, pyruvate formate lyase, diacetyl synthase, diacetyl reductase, alcohol decarboxylase, lactate dehydrogenase, pyruvate dehydrogenase, and aldehyde dehydrogenase.        Lipid degradation, modification or synthesis. Enzymes involved include lipases, esterases, phospholipases, serine hydrolases, desaturases, and linoleate isomerase.        Polysaccharide synthesis. Polysaccharides are important not only for potential immune enhancement and adhesion activity but are important for the texture of fermented dairy products. The enzymes involved are a series of glucosyl transferases, including beta-(1-3) glucosyl transferase, alpha-N acetylgalactosaminyl transferase, phosphogalactosyl transferase, alpha-glycosyl transferase, UDP-N-acetylglucosamine C4 epimerase and UDP-N-acetylglucosamine transferase.        Amino acid degradation. Enzymes include glutamate dehydrogenase, aminotransferases, amino acid decarboxylases, and enzymes involved in sulphur amino acid degradation including cystothione beta-lyase.        
Sequencing of the genomes, or portions of the genomes, of numerous organisms, including humans, animals, microorganisms and various plant varieties, has been and is being carried out on a large scale. Polynucleotides identified using sequencing techniques may be partial or full-length genes, and may contain open reading frames, or portions of open reading frames, that encode polypeptides. Putative polypeptides may be identified based on polynucleotide sequences and further characterized. The sequencing data relating to polynucleotides thus represents valuable and useful information.
Polynucleotides and polypeptides may be analyzed for varying degrees of novelty by comparing identified sequences to sequences published in various public domain databases, such as EMBL. Newly identified polynucleotides and corresponding putative polypeptides may also be compared to polynucleotides and polypeptides contained in public domain information to ascertain homology to known polynucleotides and polypeptides. In this way, the degree of similarity, identity or homology of polynucleotides and polypeptides having an unknown function may be determined relative to polynucleotides and polypeptides having known functions.
Information relating to the sequences of isolated polynucleotides may be used in a variety of ways. Specified polynucleotides having a particular sequence may be isolated, or synthesized, for use in in vivo or in vitro experimentation as probes or primers. Alternatively, collections of sequences of isolated polynucleotides may be stored using magnetic or optical storage medium and analyzed or manipulated using computer hardware and software, as well as other types of tools.